1. Field of the Invention
The present invention relates to an image pickup apparatus for picking up an image of a subject.
2. Related Background Art
An example of a configuration of a conventional solid-state image pickup element is shown in FIG. 1. In the figure, reference numeral 101 denotes pixels having a photoelectric conversion portion such as a photo diode. A pixel area 100 on which an image of a subject is picked up is formed by arranging these pixels two-dimensionally.
In addition, reference numeral 103 denotes vertical signal lines to which signals from the pixels 101 are read out, 104 denotes storage capacitors for temporarily accumulating signals read out to the vertical signal lines 103 from the pixels 101, 105 denotes transfer MOS transistors for transferring the signals read out to the vertical signal lines 103 to the storage capacitors 104, and 106a and 106b denote transfer MOS transistors for transferring signals in the storage capacitors 104 to horizontal signal lines 107.
Moreover, reference numeral 108 denotes a vertical scanning circuit for scanning sequentially in the vertical direction each line of pixels 101 in the horizontal direction, thereby controlling to read out signals to the vertical signal line 103 from the pixels 101 on each line basis. Reference symbols 109a and 109b denote horizontal scanning circuits for controlling the transfer MOS transistors 106a and 106b, thereby sequentially reading out the signals accumulated in the storage capacitor 104 to horizontal signal lines 107a and 107b. Reference symbols 110a and 110b denote a reset MOS transistor for resetting the horizontal signal lines 107a and 107b. In addition, reference numeral 107 denotes load current sources for forming transistors and source followers included in the pixels 101.
Here, an arrangement of color filters for a conventional solid-state image pickup element will be described. FIG. 2 shows an example of the arrangement, where reference numeral 121 denotes first color filters for transmitting red light, 122 denotes second color filters for transmitting green light, and 123 denotes third color filters for transmitting blue light.
The first color filters 121 and the second color filters 122 are alternately arranged in odd columns starting from the first column of the pixel 101, and the second color filters 122 and the third color filters 123 are alternately arranged in even columns starting from the second column of the pixel 101, which color filters correspond to each of the pixels arranged two-dimensionally. Moreover, the second color filters 122 are arranged such that those in the odd columns and those in the even columns are not adjacent with each other in the horizontal direction.
The conventional solid-state image pickup element has the pixel area 100 in which a plurality of color filters are arranged as shown in FIG. 2. However, with this method, for example, if a solid-state image pickup element having 640 pixels horizontally and having 480 pixels vertically at a pixel pitch of 10 μm is used, a focal distance of a lens giving its standard angle of view is 8 mm that is a diagonal length of the solid-state image pickup element.
Therefore, there is a limitation in making the image pickup apparatus thinner, such as a digital camera upon manufacturing the apparatus using such solid-state image pickup elements.
FIG. 3 shows a solid-state image pickup element that is disclosed in Japanese Patent Application Laid-open No. 62-11264. In FIG. 3, solid-state image pickup areas 2 to 4 for picking up images of three color components of R, G and B are formed in one silicon chip 1. Next, configurations and operations of the image pickup areas 2 to 4 will be described using the image pickup area 2 as an example.
In the image pickup area 2, pixels 20 consisting of photodiodes 21 and transistors 22 for transferring signals generated in the photodiodes 21 to vertical output lines 23 are arranged in the horizontal and the vertical directions. Signals outputted to the vertical output lines 23 are sequentially outputted from output terminals 25 via horizontal output lines by transistors 24 that are on/off controlled by a horizontal shift register 27.
In addition, the three image pickup areas 2 to 4 are driven by a vertical shift register 14 via common reading-out drive line 12.
However, since image pickup areas are arranged one-dimensionally in one direction in the above-described conventional solid-state image pickup element, a chip size increases in one direction and a problem arises in making the image pickup element compact.
In addition, if an image of a subject is divided into three images by a lens and the images are picked up in respective image pickup areas, since an image pickup area 2 and an image pickup area 4 are spaced apart, deviation of images of the subject is caused.
Moreover, since a distance to a vertical shift register is different in each image pickup area, a control signal to be transmitted in a reading-out drive line has a decreased signal level due to a voltage drop if it is supplied to an image pickup area that is far apart from the vertical shift register. As a result, a level of a read out signal may vary to cause shading or color drift in an image that is finally obtained.